The element of surprise is a requirement for offensive warfare tactics. Because modern mobile warfare is highly mechanized, and security calls for movement under cover of darkness, means must be provided for the fast, orderly movement of troops, means which enable the troops of a unit to "see" each other while maintaining a very low profile toward the enemy so as to avoid surveillance by the enemy.
The requirement is blackout lighting for vehicles that can be seen by friendly troops whether dismounted or mounted, but which is not visible to observers on the ground beyond a given distance from the light source, and which cannot be observed from the air by observers above a given altitude or outside a cone of observation of a given angle and having its vertex at the light source.
As far as we know, World War II blackout lighting used incandescent lamps covered by shields or masks of varying patterns to provide the required observability limits and the required observable light patterns.